1. Field of the Invention
The present invention relates to a scattering-parameter estimation method and transceiver using the same, and more particularly, to a scattering-parameter parameter estimation method and transceiver using the same capable of cost-effectively estimating S11 parameters in a half-duplex multicarrier communication system.
2. Description of the Prior Art
Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behaviors of linear electrical network when undergoing various steady state stimuli by electrical signals.
Many electrical properties of network components may be expressed using these S-parameters, such as gain, return loss, or reflection coefficient. In the context of S-parameters, scattering refers to the way in which the traveling currents and voltages in a transmission line are affected when they meet a discontinuity caused by the insertion of a network into the transmission line. This is equivalent to the wave meeting an impedance differing from the line's characteristic impedance. For example, with respect to a communication device at one side of a link (or communication channel) with another communication device at the remote side of the same link, S11 is the input port voltage reflection coefficient, S12 is the reverse voltage gain, S21 is the forward voltage gain, and S22 is the output port voltage reflection coefficient.
In a typical power-line communication environment or channel, the S11 parameter is frequency dependent, i.e., the power-line typically has higher S11 values at some frequency components (carriers) and lower values at the others. For any signal transmitted to the power-line, more energy will be dissipated as thermal more at certain frequency components that have higher S11 values, and thus lower power is delivered to the remote side at these frequency components (i.e. lower S21). Therefore, if the signal spectrum on the line near the transmitter output is measured, power spectral density (PSD) notches can be observed, such that it is desirable for a transmission side to compensate the PSD notches according to S11 parameters over all frequency components.
According to current available standards like IEEE 1901 or G.hn (ITU-T G.9960) for power-line communication in home networking, a power line communication (PLC) device is a half-duplex multicarrier communication system, i.e. a typical cost-effective PLC transceiver can include only one processing module for either converting frequency-domain signals into time-domain signals via inverse fast Fourier transform (IFFT) during signal transmission or converting time-domain signals into frequency-domain signals via fast Fourier transform (FFT) during signal reception at different time slots. Although the S11 parameter calculation or estimation is well known in traditional communication or circuitry theory, there is still lack of a cost-effectively method for estimating S11 parameters in such half-duplex multicarrier communication device. Thus, there is a need for providing a cost-effectively method for estimating S11 parameters in the power line communication system.